1. Field of the Invention
The invention is concerned with a storage device with variable storage capacity, in particular for storing rod-shaped products, with an input area, an output area and also a continuous conveying element connecting the input area to the output area, in such a way that the storage device operates on the principle of “first in-first out” (FiFo store). The conveying element, which is guided by way of guide elements in a loop from the input area to the output area, has a multi-layered storage area, normally provided with products, namely a so-called full strand, and a multi-layered return area, normally free of products, namely a so-called empty strand. The two areas being compensated in length, depending on the state of fullness of the storage device, in such a way that the overall length of the conveying element is constant.
2. Discussion of Background Information
Storage devices of this kind are used in particular in the domain of the tobacco-processing industry and connect production machines, e.g., a cigarette-making machine—also designated below as a “maker”—to a cigarette-packing machine—also designated below as a “packer”. The task of the storage device is to bridge short stoppage times of the maker or packer without the entire production line having to be halted. In this way, continuous production is guaranteed. During operation of the production line, the state of fullness of the storage device changes as a function of breakdown or stoppage times of individual components. In the event that e.g., the packer, which is arranged downstream of the storage device, breaks down, the storage device fills to a storage maximum in that the length of the full strand increases with simultaneous shortening of the empty strand. If the maker connected upstream of the storage device breaks down, operation of the production line is maintained at least temporarily in that the packer receives the products from the storage device until the storage minimum has been reached. Owing to the constant release of products from the storage device—with a simultaneous lack of delivery of products into the storage device—the length of the full strand is reduced, while the length of the empty strand lengthens correspondingly, so the overall length of the circulating conveying element is therefore always constant. The conveying element is therein wound in a loop to create as long as possible a storage or transport path.
In a known storage device, the full strand and the empty strand are arranged above one another, i.e., in different planes from one another. Therefore two guide elements necessary for guiding and reversing the conveying element are needed in each case both for the full strand and for the empty strand. The conveying element also has to be steered from the lower to the upper plane and back, requiring additional structural outlay. On the one hand, this has the disadvantage that the known storage device has a great overall height, making it difficult or completely impossible to use, especially in factory halls with a low ceiling height. On the other hand, maintenance or servicing of a storage device of this kind is very complicated, as individual parts are sometimes difficult to access. Furthermore, the known storage device has a great multiplicity of parts, leading to high manufacturing costs.
The same applies to a further known storage device in which the full strand and the empty strand are basically arranged side by side. However, the full strand and the empty strand superimpose one another or cross one another in the area of a common guide element, so that the full strand and the empty strand are arranged above one another at least in the area of the common guide element. This has, on the one hand, the disadvantage that the overall height of the known storage device is considerable and, indeed, is conditional on layering, either in blocks or alternately, of the individual windings of the full strand and the empty strand in the area of the common guide element. On the other hand, the known structure requires a multiplicity of reversals or reversing devices, leading to a great multiplicity of parts.